In 3rd Generation Partnership Project (3GPP) that is a standardization project, a standardization process for Evolved Universal Terrestrial Radio Access (which is hereinafter referred to as EUTRA) that realizes high-speed communication has been performed by employing flexible scheduling in prescribed frequency or time units, which is referred to as an orthogonal frequency-division multiplexing (OFDM) communication scheme or a resource block.
Furthermore, in 3GPP, discussions on Advanced EUTRA that realizes higher-speed data transfer have taken place. As one technology relating to Advanced EUTRA, carrier aggregation (CA) is employed. The carrier aggregation is a technology in which multiple different frequencies (which are referred to as component carriers (CCs)) are aggregated for use and thus a transfer rate is improved (NPL 1, Chapter 5.5).
Furthermore, a terminal device that is communicating with a base station apparatus using the carrier aggregation groups frequencies (component carriers) of one or multiple cells and manages a state of an uplink transmission timing (Timing Advance (TA)) for every group. The group in which the uplink transmission timing indicates the frequencies (the component carriers) of the same cell is also referred to as a timing alignment group (TAG) (NPL 1, Chapter 10.1.2.7).
In EUTRA, a network is mainly assumed in which the base station apparatuses have almost the same cell constitution (cell size). However, in Advanced EUTRA, a network (heterogeneous wireless network or heterogeneous network) is assumed in which the base station apparatuses (the cells) having different constitutions are present in a mixed manner in the same area and a control method that is adapted for this network has been under study.
A technology (dual connectivity), in which, as in the heterogeneous network, in a communication system in which a cell (a macro cell) with a large radius and a cell (a small cell) with a radius smaller than that of the macro cell are arranged in a mixed manner, the terminal device makes connections to multiple cells of the base station apparatus at the same time and performs communication (NPL 2), has been under study.
Furthermore, in the base station apparatus, one cell is constituted by combining one downlink component carrier and one uplink component carrier. Moreover, in the base station apparatus, one cell can be constituted as only one downlink component carrier.